This invention relates to the use of mordenite zeolites as catalysts in the alkylation or transalkylation of aromatic compounds t produce cumene, ethylbenzene and other alkylated benzenes.
Cumene, also known as isopropylbenzene, is useful for the production of phenol, acetone and alphamethylstyrene. Ethylbenzene is useful in the production of styrene. Various processes for their manufacture are known.
Various processing schemes comprising alkylation and/or transalkylation reactions are known to produce monoalkylaromatic products such as cumene or ethylbenzene in high yields. However, existing processes are not without problems including the production of undesirable by-products. Examples of such by-products produced in conjunction with cumene include alkylating agent oligomers, heavy polyaromatic compounds and unwanted monoalkylated and dialkylated compounds such as n-propylbenzene, butylbenzenes and ethylbenzene. The production of unwanted xylenes are a particular problem in the production of ethylbenzene. Another problem with existing processes concerns the use of Friedel Crafts catalysts such as solid phosphoric acid or aluminum chloride. The phosphoric acid catalysts generally require the use of a water co-feed which produces a corrosive sludge by-product. Problems concerning the sludge by-product can be avoided by the use of zeolite catalysts.
It is known that aromatic hydrocarbons can be alkylated in the presence of acid-treated zeolite. U.S. Pat. No. 4,393,262 (1983) teaches that cumene is prepared by the alkylation of benzene with propylene in the presence of a specified zeolite catalyst. U.S. Pat. No. 3,140,253, (1964) and U.S. Pat. No. 3,367,884 (1968) broadly teach the use of acid-treated mordenite for the alkylation of aromatic compounds. However, such alkylations are generally not selective with respect to site and number of substitutions. Further, catalysts are often quickly deactivated requiring timely and costly replacements or reactivation.
Thus, there remains a need for an effective process for the preparation of alkylated benzenes having minimal levels of impurities utilizing a catalyst having low negative environmental impact and long life.